Solid ink or phase change ink printers conventionally receive ink in a solid form, as pellets or ink sticks. The solid ink pellets or ink sticks are placed in a feed chute and a feed mechanism delivers the solid ink to a heater assembly. Solid ink sticks are either gravity fed or urged by a spring through the feed chute toward a melt plate in the heater assembly. The melt plate melts the solid ink impinging on the plate into a liquid that is delivered to a print head for jetting onto a recording medium. Ink sticks for phase change ink printers have historically included bottom and side keying surfaces by which corresponding chutes and feed mechanisms (i.e., “ink loaders”) of the printers guide or coax the ink sticks into optimal feed/melt positions. In horizontal or near horizontal ink loaders, gravity influences the ink stick positions as the ink sticks lean against chute walls or special side-rails. Special guides have even been incorporated into the bottoms of some ink sticks to facilitate their movement over corresponding bottom-rails of some horizontal feed ink loaders. Such guides, coupled with gravity, have typically worked reasonably well to properly position and orient the ink sticks for feeding to the heater plates. In such situations, the sides of the keying features have typically included the ink surfaces contacting the guides. Such guide and key integration has undesirably limited the keying features in that insertion exclusivity has not been the only function that the keying features have been relied upon to provide. In many cases, size, placement, and configuration of keying features has been as much a function of guidance requirements as keying considerations. Keying for insertion is typically intended to allow differentiation between colors and different product models, which can include marketing programs such as contractual or retail pricing of the ink, thus aside from guiding and support functions, the keying offers opportunity to exclude inappropriate colors or models of ink from being inserted in a given ink loader.
Meanwhile, conventional keying and guide features have been even less effective in vertical ink loaders as the ink sticks have been somewhat position/orientation influenced but in most cases have not been sufficiently constrained to properly feed to the heat plates. Some vertical ink loader guidance systems have even allowed their ink sticks to misalign to extents that they have rotated and jammed. Consequently, most phase change ink printers accommodating multiple ink sticks of each of various colors and incorporating heat plates have used horizontal rather than vertical ink loader systems.
Keying features for use in many horizontal ink loader systems have been focused on a two vector interface with the ink loader: one surface for insertion and another for feed, with the former surface typically transverse to the latter. In addition to relying on gravity, such sticks are typically made more complex in shape due to color and product series (model or model range) key features running in one direction and guidance elements or surfaces running in another. The large amount of stick geography devoted to color keying in historical ink stick designs has undesirably limited the flexibility and extensibility in product series key features. As with the ink loaders, making design changes to the complex shapes of such ink sticks can introduce undesirable risks of ink stick failure from stress fracturing and variations in cooling deformation, can undesirably increase tooling cost/complexity, and/or can undesirably increase product development times.
Thus, guidance in the afore-noted cases has relied primarily on combinations of ink stick surfaces including keying surfaces not designed or intended solely for guidance. Another shortcoming of conventional loaders is that insertion keying, including model or series keying, changes from product to product to ensure marketing, operational parameter, or formulation differentiation. Parts internal to the loader, such as push blocks, change in addition to the external key plates. As a result of the historical lack of uniformity in keying schemes and the integration of guidance and keying systems, each new phase change ink printer model has typically needed a new loader configuration, which has undesirably increased ink delivery costs and product development times.
Orienting an ink loader vertically could potentially improve usability and lower cost. A vertical loader could provide the benefit of using gravity as the primary force to move or feed the ink stick. While guides in horizontal loaders typically emphasize load bearing support, such load bearing would not be required by a vertical loader. However, as noted above, conventional ink shapes are not compatible with vertical loading. Conventional ink shapes are also not compatible with an insertion direction that is in-line with or parallel to the feed direction. Ink sticks used in loaders with independent insertion and feed directions, irrespective of loader orientation or ink feed to gravity, suffer from a lack of simplified extensibility in creating independence between color, model, support, guidance and feed keying.
Thus, there is a need for phase change ink printer ink sticks having independent guidance and keying features such that the flexibility and extensibility of the keying features may be better optimized, and there is a further need for ink sticks having keying features that can be compatible with parallel insertion and feed to facilitate vertical loading or alternative loaders with feed orientation that may range from horizontal to vertical whether or not insertion is in the feed direction.